Field of the Invention
The invention relates to polymers that can be degraded or depolymerized into component units via a deprotection reaction. More specifically, the invention relates to such polymers that include hydroxymethyl-substituted aniline building blocks. These polymers are functionalized with various protecting groups, which upon deprotection, promote fast degradation of the polymer via a chain-shattering mechanism.
Description of Related Art
Degradable polymers have been known for some time, and initially were sought for long-term biodegradable applications. Recently, polymers that are capable of decomposition under specific conditions have been of interest, and specifically, so called “self-immolative” polymers have received significant attention. Self-immolative polymers are typically composed of a repeating unit that is capped at one end with a functional group which is selectively reactive under specific conditions, i.e. a protecting group. Upon removal of the protecting group, the polymer degrades from one end to the other in a head to tail fashion.
Various approaches to the design, synthesis and de-polymerization of self-immolative polymers have been proposed. Several research groups have reported success with self-immolative polymers that contain repeating hydroxymethylaniline units and a protected terminal amine. When these polymers are subjected to deprotection conditions, the protecting group is removed from the terminal amine and the degradation propagates through the polymer backbone. The key building blocks of these self-immolative polymers are 2- or 4-hydroxymethylanilines, structures that allow the 1,4- or 1,6-elimination necessary for degradation. Although, in some cases, the release of CO2 is the driving force for the degradation of the polymer backbone, the head to tail propagation is a slow process.
Self-immolative oligomers containing an amine-protected 2,4-bis(hydroxymethyl)aniline backbone have also been reported. A major limitation of this system is the necessity for the oligomer to be synthesized in a stepwise fashion; polymerization to obtain long chains of repeating units is not feasible.
A polymer able to immediately degrade in the presence of an external stimuli, thereby releasing repeating units that may comprise chemically or biologically useful compounds would find utility in numerous fields of science and technology.